Sear mechanism for guns



Nov. 27, 1934.

R. C. COUPLAND SEAR MECHANISM FOR GUNS Filed Aug. 2, 1932 Hal 2Sheets-Sheet l 36 Inventnr- Richard fijuupland Attnrney Nov, 27, 1934. CUPLAND 1,981,855

SEAR MECHANISM FOR GUNS Filed Aug. 2, 1932 2 Sheets-Sheet 2 l) WNW! ,9

Inventor" Richard fijuupland Attur'nE-y Patented Nov. 27, 1934 I g1,981,855 VSEAVRMZECHANISM FOR GUNS y i Richard 0. Coupland, UnitedNorfolk, Va.

States Army,

1 Application August 2, 1932, SerialNo. 627,244 10 Claims. (01. 89 27)(Granted under the act of March 3,1883} as V amended April so, 1928; 370o. G. 757) '5 This invention relates to a sear mechanism for guns. I

In mounting fixed machine guns on aircraft, it is customary to operatethe gun by means of a trigger motor synchronized with the propeller ofthe aircraft and adapted to be placed on either side of the gun. Whenthe gun is mounted in afiexible mannera hand trigger is employed tocontrol the firing mechanism. Where one gun is to be adaptable for allof the methods of operation it is necessary that the slide forreleasingthe sear be so arranged that it can be actuated from three. differentdirections.

The principal object of this invention is to provide a sear mechanismthat will meetthe foregoing requirements with a minimum adjustment ofparts and that will be operable upon the application of asslight force.A further object of the invention isxto so arrange the sear. mechanismthat the firing pin will be able to pass through it and .strike thebufierplateof the. gun. V I

With the foregoing and other objects inlview, the inventionresides inthe novel arrangement and combination of parts and in the details of .30construction hereinafter described and claimed,

it beingunderstood that changesin the precise embodiment. of theinvention herein disclosed may be made within the scope of what isclaimed without departing from the spirit of the inven- 35 tion. 7 V M Apractical embodiment of the invention is illustrated in the accompanyingdrawings, wherein: r

Fig. 1 isa longitudinal sectional view through the receiver of a machinegun showing thefiring pin held in cockedp'os'ition by the sear. I

Fig. 2 is an enlarged longitudinal sectional view of the rear en d ofthe belt of Fig. 1.

Fig. 3 is. a view similar to Fig. 2 showing the relative position of theparts whenthe firing pin is in fired position. 2 Figs. 4 and 5 are viewsin rearelevation of the bolt corresponding respectively to Figs. 2 and3. Fig. 6 is a plan view of Fig. 4. 2 I

Figs. '7 and 8 are detail views respectively in rear and side elevationof the sear.

r Fig. -9..isa plan view of the sear.

Figs. and i1 are detail. views respectively implan .and rear-elevationof the transverse slide.

Fig. 12' shows views in rear andside elevationof the verticallymovable'slide.

Referring to the drawings by numerals of reference thereis shown thereceiver frame 5 of a machine gun within which a bolt 6 is reciprocallymounted. Within the bolt is a longituclinally disposed firing pin 7normally urged in a forward direction by means of a spring 8 housed inthe firing pin and seated on a vertical pin 9 passing through the bolt.The firing pin is cooked in a well known manner by the lever 10 when thebolt moves in recoil.

The firing pin is held in cocked position by means of a sear 11 which ismounted for vertical sliding movement in a slot 12 in the rear end ofthe bolt and is formed with ribs 13 on its opposite sides which fit ingrooves 14 in the side walls of the slot. The sear includes atransversely disposed lug l5 movable into and out of a transverselydisposed groove 16 formed in the upper surface of the firing pinadjacent its rear end. The rear face 17 of the lug is inclined to coactwith a correspondingly inclined face 18 defining the rear wall of thegroove 16in the firing On the front end of the sear is a bent finger 19the extremity of which is disposed in the groove 16' of the firing pinwhen the latter is in the cocked position as shown'in Fig. 2. In Fig. 3where the firing pin is in the firing position the extremity of thefinger rests on top of the rear end of the firing pin and serves to holdthe sear in the elevated position. 7

A pair of lugs 2020 on the sides of the sear, one below each of the ribs13 and spaced therefrom are provided for a purpose that will appearlater. A plunger 21 mounted in the upper por tion of the sear and urgedoutwardly by a spring 22 is seated against a. bar 23 rigidly carried bythe pin 9. The plunger opposes elevation of the sear, and normally tendsto depress it into engagement with the firing pin. The lower por tion ofthe seat is. formed with an opening 24 to permit the rear end of thefiring pin '7 to strike the b ufier plate 25 when the bolt has beenarrested by the buffer plate,

The rear end of the bolt is formed with a transversely disposed slot 26having grooves 2727 at its inner end. A slide 28, (Figs. 10 and 11)insertable in the grooves .27 from either side of the bolt is disposedin front of the sear. A

more or less centrally located aperture 29 in the slide permits the rearportions of the firing pin to'mov'e through "the slide. v V

A pair of spaced lugs -30 are provided on the rear face of the slide atone side of the aperture 29 and have inclined faces 3131. These lugs liein the vertical transverse plane containing the lugs 20-20 on the sear.

On the other side of they aperture 29 is a The plunger spring 34 isdisposed in the housing 32 and a pin 35 limits extrusion of the plungerunder the influence of the spring. The slide is symmetrical about alongitudinal axis so that it may be reversed and; inserted from eitherside of the bolt, depending upon the location of a synchronized triggermotor.

The lower portion of the vertical slot. 12 in the bolt includes grooves36- 36 for receiving a vertically movable slide 37. This slide isinserted from above and includes an car 38 on each side for engaging thefioor of the transverse slot 26 and limiting downward movement of theslide. The upper corners of the slide are inclined as at 39complementary to the inclined faces 31 of the lugs 30. This slide isadapted to be elevated by the hand trigger mechanism of the machine gun.

In Figs; 2 and 4,the, lug 15 on the sear is engaged in the groove 16 ofthe firing pin which is in cocked position and-the sear is preventedfrom being raised by virtue of the engagement of one of its lugs 20under the lip of the uppermost lug 30 on the slide 28. The slide 28 ismaintained in the locking position by means of the spring-pressedplunger 33. When the slide is moved laterally (to the left in Fig. 5)the lug.

30 is no longer in the path of movement of the lug 20 on the sear.

As soon as the sear is released the firing pin spring 8 moves the firingpin '7 forward, the transverse lug 15 on the sear being cammed out ofthe groove 16 in the firing pin by virtue of the coaction ofthe-inclined surfaces 17 and 18. Upon elevation of the sear the bentfinger 19 is moved out of the groove 16 and the firing pin in movingforward comes to rest with its rear end directly under the finger 19(Fig. 3). As a consequence the sear is held inthe raised positionagainst the action of the plunger 21 which tends to depress it, and itcannot be lowered into the path of the firing pin. In this position ofthe parts the lug 20 on the elevated sear isin the path of movement ofthe lug 30 on the slide 28.

As the bolt moves in recoil the cooking lever 10 retracts the firing pinagainst the tension of the firing pin spring. As soon as the finger 19is clear of the rear end of the firing pin the sear is depressed by itsspring into the groove 16. This depression of the sear moves thelug 20be-' low the lug 30 on the slide 28 and the slide under the influence ofits spring immediately moves laterally of the bolt and positions the lug30 above the lug 20 thereby locking the sear and firing pin in cockedposition.

The slide 28 is actuated directly from the side of the bolt or it. isactuated indirectly through the vertical slide 37.

I claim:

1. In a gun, a reciprocal breech bolt, a firing pin having a grooveadjacent its rear end and movable relative to the bolt, a cooking leverfor the firing pin, a vertically movable sear carried by thebolt andadapted to be elevated by the firing pin on forward movement thereof, aspring the scar and having an aperture through which the firing pin ismovable, a pair of spaced lugs on said slide in the plane of the lugs onthe sear, one of the lugs on the sear. engageable under one of the logson the slide when the sear is depressed, a plunger on the slideengageable with the sear and normally holding the slide in searin thebolt operable to move the transverse slide out of sear-locking position.

2. In a gun, a reciprocal breech bolt, a firing pin having a grooveadjacent its rear end and movable relative to the bolt, a cocking leverfor the firing pin, a vertically movable sear carried by the bolt andadapted to be elevated by the firing pin on forward movement thereof, aspring normally tending to depress the sear into engagement with thefiring pin to hold the same in cocked position, means on the seardisposed in the groove of the firing pin when cooked and engageable withthe firing pin when fired whereby the sear is held in the elevatedposition, 2, lug on each side of the sear, a transversely movable slidereversibly mounted in the bolt in front of the searv and having anaperture through which the firing pin is movable, a pair of spaced lugson said slide in the plane of the lugs on the sear, one of the lugs onthe sear engageable under one of the lugs on the slide when the sear isdepressed, and a plunger on the slide engageable with the sear and.normally holding the slide in sear-locking position.

3. In a gun, a reciprocal breech bolt, 2. firing pin having a grooveadjacent its rear end and movable relative to the bolt, a cooking leverfor the firing pin, a vertically movable sear carried by the bolt andadapted to be elevated by the firing pin on forward movement thereof, aspring normally tending to depress the sear into engagement with thefiring pin to'hold the same in cocked position, means on the seardisposed in the groove of the firing pin when cocked and engageable withthe firing pin when fired whereby the sear is held in the elevatedposition, a lug on the sear, a transversely movable slide mounted in thebolt in front of the sear and having an aperture through which thefiring pin is movable, a lug on said slide in the planeof the lug on thesear, the lugon the sear engageable under the lug on the slide when thesear is depressed, and a plunger on the slide engageable with the scar.and normally holding the slide in sear-locking position. v

4. In a gun, a reciprocal breech bolt, a firing pin movable relative tothe bolt, means for cooking the firing pin, a vertically movable searcarried by the bolt and adapted to be elevated by the firing pin onforward movement thereof, a spring normally tending to depress the searinto engagement with the firing pin, means on the sear engageable by thefiring pin whereby the sear is held in the elevated position, atransversely movable slide reversibly mounted in the bolt in front ofthe scar and having an aperture through which the firing pin is movable,and means seated on the sear for normally moving the slide into positionto engage the sear.

1.5. In a gun,.a reciprocal breech bolt, a firing .moving the slide intoposition to engage the sear. i i

6. In a gun, a reciprocal breech bolt, a firing pin movable relative tothebolt, means for cocking the firing pin, a vertically movable searcarried by the bolt andadapted to be elevated by the firing pin onforward movement thereof, a spring normally tending to depress the searinto engagement with the firing pin, means on the sear engageable by thefiring pin whereby the sear is held in the elevated positiomatransversely movable slide mounted inthe bolt in front of the sear andhaving an aperture through which the firing pin is movable, and meansfor normally moving the slide into position to engage thesear.

'7. In a gun, a reciprocal breech bolt, a firing pin movable relative tothe bolt, means for cooking the firing pin, a vertically movable searcarried by the bolt and adapted to be elevated by the firing pin onforward movement thereof, means for normally depressing the sear intoengagement with the firing pin, a finger on the sear engageable by thefiring pin when the firing pin is in forward position whereby the searis held in the elevated position, and a slide working between the searand the finger for locking the sear.

8. In a gun, a reciprocal breech bolt, a firing pin movable relative tothe bolt, means for cooking the firing pin, a vertically movable searcarried by the bolt and adapted to be elevated by the firing pin onforward movement thereof, means normally tending to depress the searinto engagement with the firing pin, a lug on each side of the sear, atransversely movable slide reversibly mounted in the bolt, a pair ofspaced lugs on the slide, one of the lugs on the sear engageable un-,der ,one of the lugs on the slide when the sear is depressed, a plungeron the slide engageable with the sear and normally holding the slide insear-locking position, and a vertically movable slide in the boltengageable with one of the lugs on the slide to move the slide out ofsear-locking position.

9. In a gun, a reciprocal breech bolt, a firing pin movable relativetothe bolt, means for cocking the firing pin, a vertically movable searcarried by the bolt andadapted to be elevated by the firing pin onforward movement thereof, means normally tending to depress the searinto engagement with the firing pin, a lug on each side of the sear, atransversely movable slide reversibly mounted in the bolt, a pair ofspaced lugs on the slide, one of the lugs on the sear engageable underone of the lugs on the slide when the sear is depressed, and a plungeron the slide engageable with the sear and normally holding the slide insear-locking position.

10. In a gun, a reciprocal bolt, a firing pin movable relative to thebolt, means for cooking the firing pin, a sear engageable with thefiring pin to hold it in cocked position, a sear-lock reversibly mountedin the bolt whereby it may be operated in reversed directions to releasethe

